Worm Composting

Worms, like cockroaches, are awesome composters. Worms are a bit different since they really feed on microbes as much as the stuff you feed them. So this is more like a traditional “composting” technique – but works wonders on kitchen scraps, just like cockroach composting. I first got into worm composting after reading Bentley Christie’s excellent site on red worm composting. In fact he sells an excellent introduction to worm composting that is far more comprehensive than what I’ll get into here. However for a great intro to the topic, yet another method of turning your kitchen waste into amazing garden compost, read on.

What is Worm Composting

Worm composting is simple – it just involves keeping a whole bunch of worms in a bin and feeding them organic scraps that you want to turn into dirt. Just like cockroaches, worms have a tremendous capacity to turn almost any kind of food source into nice rich dirt ready for the garden.

Worms are a little different in how they process food. As much as the food itself, worms feed on the microbes inhabiting it. This is an important distinction since it will help you set up a really nice worm bin. If you simply put in fresh food, worms can’t do much with it. It is tough and chewy and just not appetizing to them. But, after a little while the food gets infected with microbes that start to break it down. It starts getting mushy and really microbe-rich. Now it is really attractive to worms and they come in for a nice feed.

As worms eat this partially degraded food, their own microbes that inhabit their gut get involved. The food matter is further broken down by the action of these microbes and a nice, microbially super-active, dark brown soil-like substance is excreted. This is the precious worm casting that you are looking for.

Why Worm Composting?

Worms eat everything. They are awesome composters! Manure, coffee grounds, food scraps, meat, milk, etc all can go into the bin to be turned into worm casting compost (caveats noted in the feed section). This is important because it is one more outlet for your kitchen scraps that might not be ideal for the compost pile. For example just throwing half a pound of kitchen scraps on your compost pile every day will likely lead to a stinky, wet mess. But if you have a worm bin with a healthy population of worms, you will be able to add kitchen scraps each day, and the worms will turn them all into compost – no smell, no mess, just nice clean worm casting compost.

Worm composting provides much more benefit than just consuming your kitchen scraps however. Worm cast, or vermicompost, is called ‘black gold’ for a reason. It is a spectacular fertilizer for the garden. It has all the microbial benefits of traditional compost (high beneficial microbe counts), but also contains high levels of bio-available nutrients. The action of the worm gut microbes breaks down the nutrient rich substrate into incredibly nutritious vermicompost.

Basic Principles of Worm Composting

Worms are an awesome composter because they are so easy to keep and they eat everything. There are just a couple main points to keep in mind when raising worms:

Bin setup

Bedding material

Moisture level

Feeding

I’ll cover each of these points and then look at the worm bin in action. Worm composting is pretty easy and I’m sure most readers here are familiar, but for new folks this should be great.

The Worm Bin Setup
The ideal worm bin is a flow-through system that allows you to harvest pure worm castings without disrupting or removing the worms. If you want to purchase the ultimate worm bin, that is also very affordable, you can buy a continuous flow worm bin system – they are the best worm bin design I’ve seen. If you want to make your own system, you can make one cheaply and easily. While a less ideal system, this will work great for the beginning worm farmer.

I’ll just describe a stacking system since it’s so easy to make. Here’s how you would set it up:

Get bins that stack – ideally they would nest a bit. This is so you can get direct soil-bin contact so worms can move up. Those big plastic tote bins are perfect.

Start with the bottom bin. This has no holes in the bottom and is just there to catch the fluid that leaks out as food decomposes and you water the system.

Stack the next bin inside the first one, so it’s ‘nested’ in the first one. This second bin has many holes cut in the bottom to allow water to drain. This is your worm composting chamber. In this bin you will put the worms, their bedding and food.

As the second bin starts getting full, you will stack the third bin on top of it. Right on the top of the bedding. This bin has holes in the bottom as well. The fresh bedding and fresh food will lure the worms up into this bin.

Once all the worms are attracted to the top bin, you can remove the second, middle bin.

Now you have a bin full of awesome organic compost – worm castings!

That’s a basic worm bin system that is cheap and effective. It takes minutes to make and allows you to harvest castings without fussing about with the worms.

Now let’s look at the second main factor – the bedding.

Worm compost bedding
Worms are pretty tolerant creatures. I mean, they live in the dirt. Clearly they don’t require 5-star “digs”. But there are some things you can do with bedding to help keep your worms happy and healthy. Stick to these guidelines for bedding success.

Use a TON. You can’t have too much bedding, but you can have too little. I recommend at least 6 inches deep worth of bedding in your worm bin.

Try to use bulky bedding that doesn’t compact very easily. This will help keep the system light and aerated. Worms are aerobes they need oxygen. So keeping aerobic conditions is important. That’s why we don’t use soil – too dense and compact, it can get anaerobic easily and that’s bad for your worms.

Don’t use anything that could be toxic. This is obviously a no-brainer, but just be wary of chemicals, salts from fertilizers, stuff like that. You want nice clean bedding for your worms.

Any high carbon bedding will be great as it doesn’t break down too fast, doesn’t compact too badly, holds and drains water well, and breathes well.

Some examples of great bedding would be:

Shredded newspaper, cardboard, egg cartons

Shredded brown paper

Straw: all kinds – in the Philippines we use rice straw, in the states straw hay (ideally composted a bit already)

Coco peat/coco coir – make sure it is low sodium

Peat moss

Very aged manure – vegetarian only (horse, cow, sheep, etc)

Leaves – shredded so they don’t stick together and clump (ideally composted already)

So now you have your bin setup and you have added a ton of really good bedding. The next step is moisture level.

Worm Bin Moisture level
Worms breathe through their skin, and require a moist environment to exchange oxygen across their membrane surface. However you don’t want to drown the system and produce anaerobic conditions. Think of it like a compost pile or garden soil – nice and moist without being dripping wet.

The moist environment is not only for the worms. You are cultivating their food – microbes. This is where the compost pile analogy really makes sense. You will be adding food to the system, burying it under the substrate where it will start to decompose. You want a nice healthy aerobic microbial population to work on it just like what happens in a compost pile. If the environment is too wet, the food you added will sit in anaerobic conditions and just like when a compost pile ‘goes bad’ from being too wet, your system will go bad and stink and not be productive.

So for worm composting moisture level is like the goldilocks phenomenon – not too much and not too little. Keep the system moist by misting it every day during dry conditions, but don’t dump water on the system to make it wet. Some things you can do to keep the moisture level correct:

Ensure your worm bin has plenty of drain holes in the bottom to drain excess fluid

Don’t overload the system with food scraps

Mist only, don’t dump water on system

Mist regularly to keep system moist

Keep in mind the type of food you are adding – wet or dry – and add water accordingly

Feeding
Feeding is the most frequently questioned of the worm composting factors. How much to feed worms? How often to feed worms? WHAT to feed worms? These are all great questions when you are getting started, and fortunately the answers are pretty straightforward. One thing to note – experience helps here. As you become more experienced, you will become confident in your feeding practices. So dive in, feed those worms and learn from your mistakes. I’ll give you some tips now to get you started.

First, what to feed your worms. This is an easy one since we can just make a list:

*in moderation: these items are generally seen as BAD and never to be used in worm composting. But I don’t like something that only does 90% of the job. I want to be able to add everything to the bin for composting. So I included those items with a big warning: add these items sparingly!! Not more than 1/10th the total food added at any given time, even less for the grease, oils, and meat-eater feces.

What to feed is the easy part – almost anything. How to feed is where it gets a little more complicated. Just to give a little background, worms are attracted to the food source as it becomes infested with microbes and starts decomposing. The earthworms feed on the decomposing food source and the microbes living in it. So keep that in mind for feeding – you want a nice healthy population of microbes more than anything. Just like other forms of composting!

How often to feed compost worms? Add food every few days. How much to feed your compost worms? To start with just a little food, like less than 1/4 the weight of worms you are keeping. So the amount of food depends on the number of compost worms you have – a pound of worms may eat around 1/2 lb food per day or up to 2 lbs per day depending on species and environmental conditions.

However, I don’t like thinking in strict numbers since feed rate is such a subjective thing. Things like temperature, moisture, humidity etc can all affect the feed rate of your worms. I prefer to just watch the bin. I call it the “watch the bump” technique. When you add food to the bedding you typically dig down a few inches, put the food in and then cover the food. This creates a little mound in the bedding where there was none before. As the food decomposes and the worms eat it, the bump goes down. When I see the bump fall down, it’s time for the next food. This way you can kinda gauge how much they eat and learn the best amount to feed your worms depending on conditions.

Watch out for bad smells coming from your bin. If you smell something rotten, chances are you fed too much or got it too wet where you added the food. It’s gone anaerobic and the wrong microbes are at work. No need to panic, just back off the food and water until the system recovers. It will naturally recover without you intervening as long as you didn’t add something really toxic.

There are some things to keep in mind when feeding:

Moisture: things give off water as they break down. Especially veggies and fruits. So keep in mind when feeding that you are affecting the moisture level in the system. Avoid too much wet food at a time, so you don’t get anaerobic conditions.

It’s easy to feed too much but hard to feed too little: so don’t feed much! Especially at the start. Feed a little food to start with, and slowly work up from there as you get to know your worms’ feed capabilities.

Everything in moderation: don’t feed too much of any one thing, ideally. Mix it up and feed your worms a variety of items.

Food types: What you feed needs to break down a bit before the worms can eat it. But everything breaks down at a different rate. Be aware of what you are adding, for example things like broccoli stalks, raw carrots and things like that will take much longer to be available to the worms than something like oatmeal or fresh leaves. If you add too much wet mushy stuff you will cause anaerobic conditions but if you add only stalks and woody stuff it will take a long time to be available to the worms. Mix your feed types to achieve a balance.

The Worm Composting System in Action

Here is the step-by-step setup and operation of the worm bin. It draws from the concepts above, showing them in action.

To start your worm farm, start with the bottom bin that will catch the drippings. It is solid and has no holes, because you want to keep the liquid that drops there and feed to your compost pile/garden.

Place the next bin, this one with holes in the bottom, inside the first bin. Prop it up a bit with blocks if it nests all the way down – you need space to catch the drippings (worm leachate). You can put a piece of newspaper over the holes to cover them initially so your bedding doesn’t fall through. The paper will rot away and the liquid will drip through eventually.

Fill the second bin with your bedding. Add a good amount, 3-6 inches at least.

Now add your worms to the bedding.

Wait for a week or two before first feeding. This is just to let them get acclimated to their new habitat.

Note: You may have many worms trying to escape in the first month or two – that is fine, they are just getting used to their new home. Leave a light on above the bin if you want to discourage that.

Now add a bit of food to the bin. Dig a little hole a few inches deep in the bedding, add your food and then cover it and mist with water. This should cause a little bump in the bedding.

Start with very little food initially – it is far easier to overload the system with food than to starve your worms. You can build up as you get comfortable with the setup.

Watch the bump you made over the next several days. When it has dropped back down, add more food to the bin, in a different location.

Mist your bin when you notice the surface get dry, but you don’t need to dump water in it. The idea is to keep it moist but not super wet.

When you notice the bottom bin getting full, you can use that worm leachate on your garden. Pour it straight into your compost pile, or dilute it to use in the garden, at least 1:1 but preferably more like 1:10 with water.

Worm Composting Summary

There you go. The worm composting system for getting rid of your table wastes. Now we have yet another cheap, simple, sustainable way to eliminate your kitchen scraps while producing amazing fertilizer for the garden. What a neat way to compost! You can do this anywhere, even in your house! If you are doing things correctly, there won’t be any unpleasant odors coming from the bin.

If you haven’t started worm composting before, I hope this article helps convince you of the ease and effectiveness of this natural farming technique.

Ready to get started? You can order worms online easily. Once again you can purchase from Red Worm Composting, a trusted supplier of composting worms. If you’re ready, buy compost worms from Bentley and get started worm composting today.

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Great article Patrick! I have raised composting worms for several years and have experimented with various types of worm bins, so I have some additional suggestions.
1. Stacking plastic bins work well but obviously don’t breathe well. Holes in the bottom of inner bins allow excess moisture to drain, but additional holes in the sides and lid are important to allow for air flow. If the worms don’t get enough air to breathe, they will surge out of your bin in a mass exodus! I’m sure that you have seen all the earthworms crawling on the ground after a rainstorm. They can’t breathe with all that water in the soil. Your compost worms have the same problem when it is too damp.
2. Sometimes they will try to escape because they don’t like some food that you added. (Too much citrus, onions, or other aromatic foods may make it difficult for the worms until the microbes have enough time to start breaking them down.) This happens from time to time to everyone, so I just pull off the lid slightly to let in more air and sometimes mix in more bedding if it is too wet.
3. If you choose deep bins, it is difficult to nest them together because they get so heavy. If you want to nest them, look for the most shallow bins. The vermicompost will be damp and much heavier than the bin of fluffy bedding that you start with.
4. Many sources online say how easy it is to have stacked bins where the worms are supposed to crawl up to the upper bin where the new bedding and food is. In practice you may get many doing this but many staying behind in the bin with just the worm castings. Remember that worms feed on microbes and with a slow stream of moisture coming down from the upper bin full of microbes, they will still have a good food supply even months after you add the second bin and stop feeding the first one. I have found that it is more effective to just keep a separate second bin once the first is full. Then when the first bin has aged a bit to let the worms finish the remaining food and bedding, the castings and worms can be harvested.
5. Starting a bin, it is wise to mix in vermicompost and aged food directly to the new bedding. Fresh bedding and fresh food scraps won’t have enough microbes for the worms, especially if you are adding a lot of worms from a different bin. The better that you can start out your worms, the less likely that they will try to escape to look for a better place to live. Remember with no microbes, they starve. With not enough air, they can’t breathe.

I really appreciate you taking the time to enhance my article with your knowledge – thanks!

Those are great nuggets of wisdom for those reading this article. All good advice in my book. It’s true the bins are less ideal in many ways as you mentioned. The bins work ok for getting into vermicomposting quickly, but ideally we would use a more breathable solution, that flows through rather than convincing the worms to move. I made the mistake once of inoculating a bin with compost tea shortly before trying to get the worms to migrate – they were soooo happy just to hang out and feed on my nice tea. haha

Right on, man you are like the cavalry, I have questions and then you show up

I have been doing this for about eight months now and in the summer it was great as I have a large amount of green vegetable matter from the garden. Then when I removed the castings to start over I divided them in two and started another bin. Starting January I took to feed them lots of Japanese Green Tea with roasted rice, with other things of course but once in a while instead of adding water to my peat moss periodically I put a bunch of stuff like carrot peels and lettuce in the blender and add water that way if you know what i mean.

Then about a month ago I had probably over done it, both with moisture and food and I noticed lots, and I mean lots, of little mites who seemed to take over, and I mean, taking over. I was worried about my babies (the worms) so I did some internet research and they seem to all say the same thing: stop watering and stop feeding for some time and use some melon-cantaloup rind to attract the little buggers. They love it, the red mites and others, they say, and when they are all over you collect the fruits and drown the little guys. I freeze them in the Canadian deep freeze.

It kind or sort of worked. My mites aren’t red and they are marginally attracted to fruits (they may be Japanese tea mites
They kind of go on it but mostly to lay their eggs and of course I deep freeze that right away.
But since then I stopped feeding and I left the bins without a lid for some time and things have dried a little. There is not so many mites anymore but they are still in there deeper in the peat and the worms seem to be doing OK.

What do you think? Is there a way to get rid of the mites? I read that some mites is OK. I read that the mites are part of the system but some is one thing, the place crawling with them is another!
What do you think?

Thanks in advance and also thanks for the great Biochar article and the link, it’s been very useful to me.

Yep, no worries there. I’ve had mite explosions and pillbug explosions and all sorts of things but doesn’t usually bother the worms much. In my experience those are things that you weather and when you have the balance of food/moisture/air correct again, the mites will go away again, or at least back to normal levels. Let me know what happens with them! Sounds like they’re already back down to reasonable numbers so that’s good!

I had a mite infestation last summer when I added too many fruit scraps one week. The worms couldn’t keep up with all the food, so it gave other insects the opportunity to move in. It is healthy to have a diverse worm bin, but not if it becomes out of balance with too many mites, fruit flies, or other insects. What I did first was to stop adding food, the reason why the mites were there. I even removed some food that seemed to be getting eaten more by mites than worms. Then I added more bedding to bury the food that was left. Worms do better with buried food than mites do. Without a plentiful food source, the mites will die down to a reasonable number, but the worms will be fine for a long time on the microbes that have already broken down the food. Once the mites are less noticeable, you can slowly start adding food back. Really, that’s about all you have to do… just make it less hospitable for the mites and better for the worms.

Right on, thanks David that makes a lot of sense and it’s kind of in line with what I did instinctively, I haven’t added food since and the worms seem to just spread out all over the bins rather than congregate as they tend to do when I add food in little buried piles. It better I think as they will feed on all the piles more evenly I think.

When i first started I think I was burying the food a tad too deep and I found I had all castings at the bottom and all bedding in the layer closer to the surface if I am making any sense. Now I tend to want to keep the food closer to the surface and indeed now that the food is more scarce the worms tend to come very close to the surface. Casting is finer so should sink at the bottom hence the bedding will be used more evenly? I think I am getting a handle on how much moisture is best and thanks for dropping by reassuring me as yes I have read the mites are OK but at one point there was so many in there I just did not know what to think.

But, hey, the worms are OK, things are good. I can’t wait to start brewing compost teas when the gardening season begins, lots of fun.

Hi,
I’m about to start a worm composting system. I was wondering if i could directly feed the worms my bokashi compost? Our bokashi buckets are mainly composed of raw vegetable scraps and fruit scraps with a very small amount of bread items and occasionally yogurt. Would I have to mix in regular kitchen scraps along with the bokashi compost? I was also wondering if feeding almost finished thermal compost to the worms would be okay? I mainly want to have a worm setup so I can make the purest worm castings possible for Aerated Tea’s and not so much for doing a majority of my composting. I have a Joraform insulated composter for that along with my bokashi buckets. Thanks for sharing all this info and making this knowledgable info. I will be using your EM recipe to inoculate my own wheat bran from now on

Hi Patrick, Down here in South Africa studying an Agricultural diploma at the moment, and must say I’m loving your site and all the recipes and info ! I believe this stuff is the future ! Anyway I’v been red worm composting for years now and recently been doing an aerated worm compost tea supplemented with molasses. You guys do any aerated compost teas ? Thanks for your time

Yep we sure do, I’ve made a lot, and developed my own tea brewer to maximize yield of microbes from the tea. I will post all the info on those topics later, they are pretty huge. I’m a big believer in compost teas for introducing aerobic microbes to your garden, just haven’t tackled that big topic in the site yet.